444 HENRY C. TRACY 



conception somewhat further in stating that the thickening of the 

 tissue of the vestibule, that is, the ' knorpelartige Fassergewebe,' 

 is only a dense connective tissue and is to be considered as a 

 localized thickening of the dura mater. He denies the existence 

 of the utricular diverticulum in the anterior bony capsule. He 

 describes with more accuracy than previous writers the form and 

 relations of the perilabyrinthine spaces. He is in error, how- 

 ever, in assuming that the endolymphatic duct of the two sides 

 passes through the supracerebral canal to connect the two 

 sacculi. In agreement with Breschet; he affirms the existence of 

 the accessory bulb, but denies that it is supplied with a nerve 

 twig or connected with the ear. He also mentions the relation 

 between the tissue of the perilabyrinthine spaces and the lateral- 

 line canals. 



Retzius ('81) briefly describes the relation of the ear to the 

 swimbladder in Clupea harengus. His work essentially agrees 

 with that of Hasse, except that he was inclined to the opinion 

 that the endolymphatic ducts end blindly as in other fishes. 

 He also considers the supracerebral canal as merely a thickening 

 of the dura mater. He denies the existence of the utricular 

 diverticulum in the anterior bony capsule. 



Mathews ('86), in an investigation of the skeleton of the 

 British Clupeoids, has accurately described the bony canals and 

 capsules in the herring (Clupea harengus), the pilchard (Clupea 

 pilchardus), and the shad (Clupea alosa). He finds the pos- 

 terior capsule in the pilchard differing from that of other species 

 in that it is divided by a constriction. By cutting serial sections 

 through the whole length of the swimbladder diverticulum of 

 the herring, he demonstrates the tube to be open throughout. 



Ridewood ('91) describes the ear-swimbladder relation in the 

 British species, viz.: herring, pilchard, shad, sprat (Clupea 

 sprattus), thwaite (Culpea finata), and anchovy (Engraulis en- 

 crasicholus) . It is unnecessary to mention here the minor varia- 

 tions in structure which he found in these different species. 

 Ridewood by this paper set back the course of investigation of 

 the ear-swimbladder relation in the Clupeoids by reviving cer- 

 tain older conceptions which investigators were gradually show- 



